Temp issue remains, beyond stumped

[jerzia]

One thing I can assure you, you most likely DID have thermostat problems before your Opti. The engines you were running prior simply weren't smart enough to tell you about it (at least not COLD engine scenarios). Prior to the Optimax triple-nickle electronics, there simply was no "thermostat fault strategy".

So that meant you just ran it until it blew in most cases.

Jerzia: I'm wondering if you don't have sand built up in the recess at the center of the tuner/adapter plate. See a few like that and they were CONSTANTLY getting sand into the thermistor pin, causing binding and improper thermostat operation/closing. Like Leon said- sand will destroy them.

How would I address if that were the case?

[EuropeanAM]

Unfortunately if that's the case, you have to remove the powerhead (at a minimum) to be able to vacuum out (or blow out) the sand.

In theory, you MIGHT be able to see it with a smaller-headed bore-scope, inserted into the compressor strainer opening, aim about 1" toward front, 2" inward, and turn down. If you see another stainless and brass strainer, you're in the right place.

[Gambler69]

Why don't you test with the lower unit in a barrel? Using muff's will give you false readings. I had a temp issue on my 250hp optimax last year and it ran cooler on the muff's because of the house water temp is cool and under pressure. When using the barrel your impeller will have to do all the work. My mercury mechanic told me about this. My issue was a bad temp sensor. The issue wouldn't show up with the muff's.

[jerzia]

So it looks like I finally got this solved. After changing poppet valve, spring diaphragm, and grommet, the motor is finally getting up to propper operating temperature. Diacom also showed one thermostat was still not operating properly so I changed that as well. They do open at slightly different temps one at 129 and the other at 135, but they both settle at a constant 122-124 degrees. FINALLY! I do wonder though, after removing old poppet parts, they seem no different than the ones that are new, at least by the naked eye. The poppet seems to fit in the grommet exactly like the old one did, and the you couldn't tell the difference in the two grommets or diaphragms if they were layed side by side. Apparently something was different since changing them solved the problem I had been chasing for so long, but it sure makes me wonder why.

[JOE54]

endeavor to persevere

[EuropeanAM]

Only takes a few thousandths of an inch distortion to make them hang up, hang-open, etc. Glad to hear you've got it resolved.

[jerzia]

Only takes a few thousandths of an inch distortion to make them hang up, hang-open, etc. Glad to hear you've got it resolved.

Watching both temps come up evenly on Diacom and seeing them above 120 was like a refrigerator off my shoulders. As long as you're here, what is a good operating temp for compressor at load? It was around 87 at idle and about 107-109 under power.

[EuropeanAM]

There is no specification for that question. I've never seen one much over 125 even in really hot weather, unless there was blockage somewhere.

[jerzia]

There is no specification for that question. I've never seen one much over 125 even in really hot weather, unless there was blockage somewhere.

Thanks much!